The present invention relates to a paper machine screen.
A paper machine screen may, e.g. be used in/applied to the wet end of a paper machine for draining/filtration of paper fibrous material, thus for forming of the paper sheet (so-called sheet forming screen or forming screen).
A paper machine screen may e.g. be configured as a so-called long floating screen, i.e. as a screen with lower transverse threads having/forming long floats on the running side. Such screens are mainly used for papers with higher grammage. Screens of this kind may generally be used at all speeds with Fourdrinier machines as well as with hybrid-formers or GAP-formers. Screens of this kind are highly regarded due to their long operating time.
In paper machine screens/forming screens, e.g. two different materials, for example polyester and polyamide, may be used on the running side for forming the lower transverse threads. These two materials may, for example, be introduced in a longitudinal direction alternately behind one another on the running side, wherein the polyester is primarily useful for mechanically stabilizing the fabric, while the polyamide is used mainly to increase abrasion resistance and thus for extending the operating time. Both materials have generally different properties which are also reflected in the respective behavior of the threads within the fabric.
Fabrics/Screens are known, in which the lower transverse threads are always bound consistently or all with the same course with respect to the longitudinal threads extending in the lower fabric layer. When using different materials for the lower transverse threads, this may result, for example, in an inconsistent contact of the particular material groups/threads with the paper machine (due to the different behavior of the threads in the fabric), which may negatively affect both the running of the screen and the paper quality. In other words, the selection of the different materials is, in this case, very limited and the materials should be selected in such a way that both materials and the threads formed therefrom, respectively, behave as harmoniously as possible in the total fabric. If the both different threads and materials are badly adjusted, this may, for example, lead to a different projection on the running side by the lower transverse threads.
With fabrics/screens having consistently bound lower transverse threads made from different materials, it is possible to grind the screen level on the running side following its formation (e.g. after weaving and successive thermosetting), in order to reduce/preempt different/inconsistent projection of the lower transverse threads in a downward direction. This, however, will result in loss of material and an uneven running side may reoccur in a wet state.
A fabric is known, for example, from U.S. Pat. No. 6,244,306 B1 (see FIG. 2) or from US 2012/0145348 A1 (see FIG. 1). U.S. Pat. No. 6,244,306 B1 shows a consistent double binding of the lower transverse threads resulting in a long transverse thread float on the running side (a transverse thread float or “transverse-bridge” over seven successive lower longitudinal threads). Both binding positions are respectively separated by (exactly) one lower longitudinal thread extending over the respective lower transverse thread (in a plan view onto the lower fabric layer). US 2012/0145348 A1 too shows a consistent double binding of the lower transverse threads resulting in a long transverse thread float on the running side (a transverse thread float over ten successive lower longitudinal threads), wherein both of the binding positions of the respective transverse thread here are arranged directly next to each other, i.e. are not separated by a longitudinal thread extending over the respective lower transverse thread (in a plan view onto the lower fabric layer).
Illustratively, one aspect of various embodiments can be seen to provide a paper machine screen with a running side that is/can be formed such that it has a long operating time and/or a suitable operating behavior.
Illustratively, one additional or alternative aspect of various embodiments can be seen to provide a paper machine screen with a running side that is/can be formed such that it can ensure high paper quality, especially over a long period of time.
Illustratively, one additional or alternative aspect of various embodiments can be seen to provide a paper machine screen with a running side that is/can be formed such that it has a high mechanical stability and/or high abrasion resistance.
Illustratively, one additional or alternative aspect of various embodiments can be seen to provide a paper machine screen with a running side that is/can be formed consistently, e.g. with a substantially consistent projection of the lower transverse threads.
Illustratively, one additional or alternative aspect of various embodiments can be seen to provide a paper machine screen that can be easily produced.
Illustratively, one additional or alternative aspect of various embodiments can be seen to provide a paper machine screen that can be produced without or with relatively little loss of material.